Mainland Australia in the context of "Australia"

Afro-Eurasia (also Afroeurasia and Eurafrasia) is a landmass comprising the continents of Africa, Asia, and Europe. The terms are compound words of the names of its constituent parts. Afro-Eurasia has also been called the "Old World", in contrast to the "New World" referring to the Americas.

Afro-Eurasia encompasses 85,135,000 km (32,871,000 sq mi), 57% of the world's land area, and has a population of approximately 6.7 billion people, roughly 86% of the world population. Together with mainland Australia, they comprise the vast majority of the land in the world's Eastern Hemisphere. The Afro-Eurasian mainland is the largest and most populous contiguous landmass on Earth.

Oceania (UK: /ˌoʊsiˈɑːniə, ˌoʊʃi-, -ˈeɪn-/ OH-s(h)ee-AH-nee-ə, -⁠AY-, US: /ˌoʊʃiˈæniə, -ˈɑːn-/ OH-shee-A(H)N-ee-ə) is a geographical region including Australasia, Melanesia, Micronesia, and Polynesia. Outside of the English-speaking world, Oceania is generally considered a continent, while Mainland Australia is regarded as its continental landmass. Spanning the Eastern and Western hemispheres, at the centre of the water hemisphere, Oceania is estimated to have a land area of about 9,000,000 square kilometres (3,500,000 sq mi) and a population of around 46.3 million as of 2024. Oceania is the smallest continent in land area and the second-least populated after Antarctica.

Oceania has a diverse mix of economies from the highly developed and globally competitive financial markets of Australia, French Polynesia, Hawaii, New Caledonia, and New Zealand, which rank high in quality of life and Human Development Index, to the much less developed economies of Kiribati, Papua New Guinea, Tuvalu, Vanuatu, and Western New Guinea. The largest and most populous country in Oceania is Australia, and the largest city is Sydney. Puncak Jaya in Indonesia is the highest peak in Oceania at 4,884 m (16,024 ft).

The continent of Australia, sometimes known in technical contexts as Sahul (/səˈhuːl/), Australia-New Guinea, Australinea, or Meganesia to distinguish it from the country of Australia, is located within the Southern and Eastern hemispheres, near the Maritime Southeast Asia. The continent includes mainland Australia, Tasmania, the island of New Guinea (Papua New Guinea and Western New Guinea), the Aru Islands, the Ashmore and Cartier Islands, most of the Coral Sea Islands, and some other nearby islands. Situated in the geographical region of Oceania, more specifically in the subregion of Australasia, Australia is the smallest of the seven traditional continents.

The continent includes a continental shelf overlain by shallow seas which divide it into several landmasses—the Arafura Sea and Torres Strait between mainland Australia and New Guinea, and Bass Strait between mainland Australia and Tasmania. When sea levels were lower during the Pleistocene ice age, including the Last Glacial Maximum about 18,000 BC, they were connected by dry land into the combined landmass of Sahul. The name "Sahul" derives from the Sahul Shelf, which is a part of the continental shelf of the Australian continent. During the past 18,000 to 10,000 years, rising sea levels overflowed the lowlands and separated the continent into today's low-lying arid to semi-arid mainland and the two mountainous islands of New Guinea and Tasmania. With a total land area of 8.56 million square kilometres (3,310,000 sq mi), the Australian continent is the smallest, lowest, flattest, and second-driest continent (after Antarctica) on Earth. As the country of Australia is mostly on a single landmass, and comprises most of the continent, it is sometimes informally referred to as an island continent, surrounded by oceans.

Southeast Asia is the geographical southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of mainland Australia, which is part of Oceania. Southeast Asia is bordered to the north by East Asia, to the west by South Asia and the Bay of Bengal, to the east by Oceania and the Pacific Ocean, and to the south by Australia and the Indian Ocean. Apart from the British Indian Ocean Territory and two out of 26 atolls of the Maldives in South Asia, Maritime Southeast Asia is the only other subregion of Asia that lies partly within the Southern Hemisphere. Mainland Southeast Asia is entirely in the Northern Hemisphere. Timor-Leste and the southern portion of Indonesia are the parts of Southeast Asia that lie south of the equator.

The region lies near the intersection of geological plates, with both heavy seismic and volcanic activities. The Sunda plate is the main plate of the region, featuring almost all Southeast Asian countries except Myanmar, northern Thailand, northern Laos, northern Vietnam, and northern Luzon of the Philippines, while the Sunda plate only includes western Indonesia to as far east as the Indonesian province of Bali. The mountain ranges in Myanmar, Thailand, Peninsular Malaysia, and the Indonesian islands of Sumatra, Java, Bali, Lesser Sunda Islands, and Timor are part of the Alpide belt, while the islands of the Philippines and Indonesia as well as Timor-Leste are part of the Pacific Ring of Fire. Both seismic belts meet in Indonesia, causing the region to have relatively high occurrences of earthquakes and volcanic eruptions, particularly in the Philippines and Indonesia.

This is a list of sovereign states and dependent territories in the geographical region of Oceania. Although it is mostly ocean and spans many tectonic plates, Oceania is occasionally listed as one of the continents.

Most of this list follows the boundaries of geopolitical Oceania, which includes Australasia, Melanesia, Micronesia, and Polynesia. The main continental landmass of Oceania is Australia.

Tasmania (/tæzˈmeɪniə/; palawa kani: Lutruwita) is an island state of Australia. It is located 240 kilometres (150 miles) to the south of the Australian mainland, and is separated from it by the Bass Strait. The state encompasses the main island of Tasmania, the 26th-largest island in the world, and the surrounding 1000 islands. It is Australia's smallest and least populous state, with 573,479 residents as of June 2023. The state capital and largest city is Hobart, with around 40% of the population living in the Greater Hobart area. Tasmania is the most decentralised state in Australia, with the lowest proportion of its residents living within its capital city.

Tasmania's main island was first inhabited by Aboriginal peoples, who today generally identify as Palawa or Pakana. It is believed that Aboriginal Tasmanians became isolated from mainland Aboriginal groups around 11,700 years ago, when rising sea levels formed Bass Strait.

New Guinea (Tok Pisin: Niugini; Hiri Motu: Niu Gini; Indonesian: Papua, fossilized Nugini, also known as Papua or historically Irian) is the world's second-largest island, with an area of 785,753 km (303,381 sq mi). It has the third-largest remaining rainforest globally, and the highest plant biodiversity of any island. Located in Melanesia in the southwestern Pacific Ocean, the island is separated from Australia by the 150-kilometre (81-nautical-mile; 93-mile) wide Torres Strait, though both landmasses lie on the same continental shelf, and were united during episodes of low sea level in the Pleistocene glaciations as the combined landmass of Sahul. Numerous smaller islands are located to the west and east. The island's name was given by Spanish explorer Yñigo Ortiz de Retez during his maritime expedition of 1545 because of the perceived resemblance of the indigenous peoples of the island to those in the African region of Guinea.

The eastern half of the island is the major land mass of the nation of Papua New Guinea. The western half, known as Western New Guinea, forms a part of Indonesia and is organized as the provinces of Papua, Central Papua, Highland Papua, South Papua, Southwest Papua, and West Papua. The two major cities on the island are Port Moresby and Jayapura.

Bass Strait is a strait separating the island state of Tasmania from the Australian mainland (more specifically the coast of Victoria, with the exception of the land border across Boundary Islet). The strait provides the most direct waterway between the Great Australian Bight and the Tasman Sea, and is also the only maritime route into the economically prominent Port Phillip Bay.

Formed 8,000 years ago by rising sea levels at the end of the last glacial period, the strait was named after English explorer and physician George Bass (1771–1803) by European colonists.